1. Proton pump inhibition induces autophagy as a survival mechanism following oxidative stress in human melanoma cells.
- Author
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Marino ML, Fais S, Djavaheri-Mergny M, Villa A, Meschini S, Lozupone F, Venturi G, Della Mina P, Pattingre S, Rivoltini L, Codogno P, and De Milito A
- Subjects
- Acetylcysteine pharmacology, Adaptor Proteins, Signal Transducing metabolism, Apoptosis Regulatory Proteins genetics, Apoptosis Regulatory Proteins metabolism, Autophagy-Related Protein 5, Beclin-1, Cell Cycle Proteins, Cell Line, Tumor, Humans, Hydrogen-Ion Concentration, Melanoma metabolism, Membrane Proteins genetics, Membrane Proteins metabolism, Microtubule-Associated Proteins genetics, Microtubule-Associated Proteins metabolism, NADPH Oxidases metabolism, Phosphoproteins metabolism, Phosphorylation, Reactive Oxygen Species metabolism, Ribosomal Protein S6 Kinases, 70-kDa metabolism, Signal Transduction, TOR Serine-Threonine Kinases metabolism, Antineoplastic Agents therapeutic use, Autophagy, Esomeprazole therapeutic use, Melanoma drug therapy, Oxidative Stress, Proton Pump Inhibitors therapeutic use
- Abstract
Proton pump inhibitors (PPI) target tumour acidic pH and have an antineoplastic effect in melanoma. The PPI esomeprazole (ESOM) kills melanoma cells through a caspase-dependent pathway involving cytosolic acidification and alkalinization of tumour pH. In this paper, we further investigated the mechanisms of ESOM-induced cell death in melanoma. ESOM rapidly induced accumulation of reactive oxygen species (ROS) through mitochondrial dysfunctions and involvement of NADPH oxidase. The ROS scavenger N-acetyl-L-cysteine (NAC) and inhibition of NADPH oxidase significantly reduced ESOM-induced cell death, consistent with inhibition of cytosolic acidification. Autophagy, a cellular catabolic pathway leading to lysosomal degradation and recycling of proteins and organelles, represents a defence mechanism in cancer cells under metabolic stress. ESOM induced the early accumulation of autophagosomes, at the same time reducing the autophagic flux, as observed by WB analysis of LC3-II accumulation and by fluorescence microscopy. Moreover, ESOM treatment decreased mammalian target of rapamycin signalling, as reduced phosphorylation of p70-S6K and 4-EBP1 was observed. Inhibition of autophagy by knockdown of Atg5 and Beclin-1 expression significantly increased ESOM cytotoxicity, suggesting a protective role for autophagy in ESOM-treated cells. The data presented suggest that autophagy represents an adaptive survival mechanism to overcome drug-induced cellular stress and cytotoxicity, including alteration of pH homeostasis mediated by proton pump inhibition.
- Published
- 2010
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